Present-day lane change warning functions, which shall warn of approaching traffic within a warning zone on the immediately adjacent neighboring lane, typically use a predefined fixed lane width. Knowledge of the lane width is essential to limit the warning zone, which shall only extend to the adjacent lane. Such an approach of using a fixed lane width is not able to adapt to changed environmental conditions. In particular, there is a large variation of the lane width as well as the number of lanes, in different regions world-wide or even within a country, e.g. on motorways and on construction sites. Thus, a warning zone approach based on a predefined fixed lane width leads to misjudgements of the driving situation on very narrow or very broad streets or lanes, because the warning zone is dimensioned too large or too small. This can lead to false-positive warnings (i.e. a warning is issued although there is no object on the neighboring lane, for example when the actual lane width is narrower than the fixed warning zone width, then a warning might be triggered by a vehicle on the next lane beyond the adjacent or neighboring lane), and false-negative lack of warnings (i.e. no warning is issued although there actually is a vehicle on the adjacent lane, for example when the actual lane width is wider than the fixed warning zone width then a vehicle on the adjacent lane might be erroneously evaluated as being on the next lane beyond the adjacent lane).